// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/synchronization/waitable_event.h"

#include <stddef.h>
#include <windows.h>

#include <utility>

#include "base/logging.h"
#include "base/numerics/safe_conversions.h"
#include "base/threading/thread_restrictions.h"
#include "base/time/time.h"

namespace base {

WaitableEvent::WaitableEvent(ResetPolicy reset_policy,
    InitialState initial_state)
    : handle_(CreateEvent(nullptr,
        reset_policy == ResetPolicy::MANUAL,
        initial_state == InitialState::SIGNALED,
        nullptr))
{
    // We're probably going to crash anyways if this is ever NULL, so we might as
    // well make our stack reports more informative by crashing here.
    CHECK(handle_.IsValid());
}

WaitableEvent::WaitableEvent(win::ScopedHandle handle)
    : handle_(std::move(handle))
{
    CHECK(handle_.IsValid()) << "Tried to create WaitableEvent from NULL handle";
}

WaitableEvent::~WaitableEvent()
{
}

void WaitableEvent::Reset()
{
    ResetEvent(handle_.Get());
}

void WaitableEvent::Signal()
{
    SetEvent(handle_.Get());
}

bool WaitableEvent::IsSignaled()
{
    return TimedWait(TimeDelta());
}

void WaitableEvent::Wait()
{
    base::ThreadRestrictions::AssertWaitAllowed();
    DWORD result = WaitForSingleObject(handle_.Get(), INFINITE);
    // It is most unexpected that this should ever fail.  Help consumers learn
    // about it if it should ever fail.
    DCHECK_EQ(WAIT_OBJECT_0, result); // << "WaitForSingleObject failed";
}

bool WaitableEvent::TimedWait(const TimeDelta& max_time)
{
    base::ThreadRestrictions::AssertWaitAllowed();
    DCHECK_GE(max_time, TimeDelta());
    // Truncate the timeout to milliseconds. The API specifies that this method
    // can return in less than |max_time| (when returning false), as the argument
    // is the maximum time that a caller is willing to wait.
    DWORD timeout = saturated_cast<DWORD>(max_time.InMilliseconds());

    DWORD result = WaitForSingleObject(handle_.Get(), timeout);
    switch (result) {
    case WAIT_OBJECT_0:
        return true;
    case WAIT_TIMEOUT:
        return false;
    }
    // It is most unexpected that this should ever fail.  Help consumers learn
    // about it if it should ever fail.
    NOTREACHED() << "WaitForSingleObject failed";
    return false;
}

// static
size_t WaitableEvent::WaitMany(WaitableEvent** events, size_t count)
{
    base::ThreadRestrictions::AssertWaitAllowed();
    HANDLE handles[MAXIMUM_WAIT_OBJECTS];
    CHECK_LE(count, static_cast<size_t>(MAXIMUM_WAIT_OBJECTS))
        << "Can only wait on " << MAXIMUM_WAIT_OBJECTS << " with WaitMany";

    for (size_t i = 0; i < count; ++i)
        handles[i] = events[i]->handle();

    // The cast is safe because count is small - see the CHECK above.
    DWORD result = WaitForMultipleObjects(static_cast<DWORD>(count),
        handles,
        FALSE, // don't wait for all the objects
        INFINITE); // no timeout
    if (result >= WAIT_OBJECT_0 + count) {
        DPLOG(FATAL) << "WaitForMultipleObjects failed";
        return 0;
    }

    return result - WAIT_OBJECT_0;
}

} // namespace base
